Nitrofurantoin Pregnancy and Breastfeeding Warnings
Nitrofurantoin Pregnancy Warnings
FDA pregnancy category: B Nitrofurantoin should be used during pregnancy only if clearly needed; use of nitrofurantoin is contraindicated at term (38 to 42 weeks gestation), during labor and delivery, and when onset of labor is imminent. Comments: Contraindicated because of possibility of hemolytic anemia due to immature erythrocyte enzyme systems (glutathione instability)
Animal studies have failed to reveal evidence of fetotoxicity or teratogenicity except when administered in very high doses. There are no controlled data in human pregnancy. Nitrofurantoin-induced congenital anomalies have not been reported to date. One retrospective review of 91 pregnancies involving nitrofurantoin use reported no evidence of association to fetal adverse effects. In a review of 229,101 deliveries to Michigan Medicaid patients, there were 1292 first-trimester exposures to nitrofurantoin and 9998 exposures anytime during pregnancy. A total of 52 birth defects (55 expected) was reported with first-trimester exposure and included (observed/expected) 15/12 cardiovascular defects, 1/0 oral clefts, 4/3 polydactyly, 3/2 limb reductions, and 5/3 hypospadias. FDA pregnancy category B: Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.
Nitrofurantoin Breastfeeding Warnings
Nitrofurantoin is excreted into human milk. Nitrofurantoin is considered compatible with breast-feeding by the American Academy of Pediatrics, although there is a theoretical risk of hemolytic anemia in neonates and G-6-PD-deficient infants. The manufacturer recommends that due to the potential for serious adverse effects in infants less than one month old, a decision should be made to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
A study of 4 lactating women indicated that nitrofurantoin is actively transported into breast milk, achieving a milk-to-serum ratio of 6.21. The infant dose was estimated to be approximately 6% of the maternal dose or 0.2 mg/kg/day (based on a maternal dose of 100 mg nitrofurantoin macrocrystals twice daily).
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